The invention relates to using a computerized analysis of bowel sounds recorded using an electronic sound input device to diagnose gastrointestinal complaints of pain, bloating, or alteration of bowel habits, with emphasis on the diagnosis of irritable bowel syndrome.
Irritable bowel syndrome is characterized by bowel irregularity (constipation and/or diarrhea), gaseous distention and abdominal pain. Irritable bowel syndrome is the most common gastrointestinal complaint for which patients seek medical care, accounting for 30 to 50 percent of the gastrointestinal complaints that bring patients to a physician. Various studies indicate that patients with irritable bowel syndrome constitute a large portion of a typical family physician's practice and account for more than 25% of all gastrointestinal referrals. Irritable bowel syndrome is listed as a primary diagnosis in about 96,000 patients per year treated in nonfederal hospitals, and the disorder was considered a secondary diagnosis in another 85,000 patients. Most patients with gastrointestinal complaints are subjected to a battery of laboratory studies. These usually include sigmoidoscopy, complete blood count, erythrocyte sedimentation rate, serum electrolytes, liver function tests, urinalysis, and stool examination for occult blood and parasites. For a patient with chronic or recurring symptoms, endoscopy or radiographic contrast evaluations can be performed (but should not be repeated unless there is objective evidence of a change in the clinical condition, such as blood in the stool).
Since most patients with irritable bowel syndrome do not require hospitalization, these figures indicate only a fraction of the social and economic burden this condition places on patients and the health care system.
In western societies, irritable bowel syndrome occurs twice as often in women as in men. About half of the patients are first seen for this condition before they reach 35 years of age. Various studies indicate that almost half of the patients are between the ages of 35 and 49, although symptoms usually begin much earlier and are likely to continue throughout life. The true prevalence of irritable bowel syndrome may be reflected in several non-patient surveys in which as much as 20 percent of the general population reported symptoms consistent with this disorder. The majority of these people do not seek medical assistance, although it is possible that their symptoms could be alleviated through education, simple methods of stress reduction, and dietary changes.
In some patients with the irritable bowel syndrome, the intraluminal contents appear to have an unusually rapid transit time through the length of the small intestine and colon. The syndrome is a well-recognized clinical entity but does not yet have a pathophysiological counterpart because no etiologic agents have been identified and no structural or biochemical defect has been determined. Indeed, other terms for the disease include spastic colitis, mucous colitis, and the irritable colon syndrome. Affected patients generally complain of generalized abdominal discomfort. Other common symptoms include audible bowel noises, cramping abdominal pain, urgency to defecate, and the passage of loose stools, often covered with mucus but free of blood.
The symptoms of irritable bowel syndrome may be exacerbated by any factor that increases gastrointestinal motility, such as ingestion of large or fatty meals (gastrocolic reflex), medication, hormonal changes that occur at menses (increased prostaglandin E2 release), and psychological stress. Foods and beverages that produce gas (e.g., beans, cabbage) or stimulate intestinal action (e.g., caffeinated beverages) may also exacerbate this disorder.
The differential diagnosis should include other conditions that produce similar changes in bowel habits, particularly ulcerative colitis, granulomatous enteritis (Crohn's disease), and infectious diseases of the small and large intestines. (The term "differential diagnosis" refers to a group of most likely diagnoses that have the same or similar symptoms and therefore could be confused with one another.) Lactase deficiency is often associated with similar symptoms, but these disappear when the offending disaccharide is removed from the diet. Low-grade, intermittent mechanical obstruction of the small intestine may produce symptoms that are very difficult to distinguish from those of the irritable bowel syndrome. The diagnosis must always be based on exclusion of other possible illnesses, and the physician should be on the alert for changes in symptoms which may indicate some other illness, such as a serious organic disease.
The irritable bowel syndrome is understood as a motility disorder involving the small and large intestines. Although the human intestine is relatively inaccessible to investigation, several physiologic characteristics have been discovered that distinguish patients with irritable bowel syndrome from healthy individuals. Abnormalities in colonic motor activity noted in irritable bowel syndrome include an altered gastrocolonic motor response, an exaggerated colonic motor response to pain, stress, or hormonal stimulation, and increased sensation and motor activity in response to balloon distention of the rectosigmoid region. Similarly, abnormalities in motor activity of the small bowel noted in irritable bowel syndrome include exaggerated motor response to fatty meals, ileal balloon distention, or hormonal stimulation, altered ileocecal transit and an increase in motility patterns during fasting. These basic studies of motility have recently been extended using 24-hour ambulatory monitoring systems measuring motility in the small bowel. These studies confirm the presence of dysmotility in irritable bowel syndrome patients compared to normal patients.
Previous methods of performing motility studies involved colonic intubation with a multi-lumen catheter with side hole manometric ports after colonic lavage (e.g. with a high osmolarity solution, such as, GoLYTELY). These studies are particularly difficult to perform when evaluating treatment strategies for irritable bowel syndrome. The nature of the measurements have restricted application of these methods to small numbers of patients, and the overlap in the measurements between normal and irritable bowel syndrome populations is great, further complicating analysis of the studies.